Desperation is never a good mental place for problem solving. When you feel things slip through your fingertips or careen out of control, you often act out of impulse rather than thoughtfulness. This is the space where some friendship problems try to be solved - when feelings are hurt and emotions are elevated over the potential loss of a friend.
Friendships are complex for adults and kids. Feeling included is key to being a part of the community so, when someone feels excluded, it can cause an extreme response. What I have found is that children often times assume (and act as though) "if we aren't best friends, we're enemies." Exclusion can lead to hurt which leads to anger. I tried to teach my students that there is a lot of space between "best friends" and "not friends," and, in fact, this is where the vast majority of our relationships live. There are many people with whom we get along fine but wouldn't seek out on the weekend. Alternatively, there are very few people who I may be actively upset with instead of just indifferent. By allowing friendships to sit along a continuum, it takes the pressure of needing to be "best friends" or be attached at the hip. We can be frustrated without damaging our friendship, we can play with other people, and we can simply enjoy working in class together without being on one end of the spectrum or the other.
By avoiding extremes, the rules around friendship become more flexible. Kids identify friendships differently, and start to see with optimism that many people like them even if they don't feel exactly like "best friends."